Ion generating element, and ion generating apparatus equipped with same

ABSTRACT

An ion generating element includes a positive ion discharger for generating positive ions and a negative ion discharger for generating negative ions. The ion dischargers are arranged separately from and independently of each other with a distance securing insulation between them. At least one of the dischargers includes a discharging portion for causing electric discharge, and a conducting portion having a voltage same as the discharging portion. The conducting portion surrounds a perimeter or part of the discharging portion. The conducting portion may surround a perimeter or part of the discharging portion so as to partition the ion dischargers from each other.

This application is a Divisional of co-pending U.S. patent applicationSer. No. 10/555,406 filed on Nov. 2, 2005, which is a National Phase ofPCT Application No. PCT/JP2004/006588 filed on May 10, 2004, whichclaims priority under 35 U.S.C. § 119(a) to Patent Application No.JP-2003-137098 filed in Japan on May 15, 2003, and to Patent ApplicationNo. JP-2004-74600 filed in Japan on Mar. 16, 2004, the entire contentsof each of the above-identified applications are hereby incorporated byreference.

TECHNICAL FIELD

The present invention relates to an ion generating element and an iongenerating apparatus that, by releasing positive and negative ions intoa space, can decompose bacteria, mold spores, toxic substances, and thelike floating in the air. The present invention also relates to anelectric appliance incorporating such an ion generating element orapparatus. Examples of such electric appliances include airconditioners, dehumidifiers, humidifiers, air purifiers, refrigerators,fan heaters, microwave ovens, washer-driers, cleaners, and sterilizersthat are used chiefly in a closed space (i.e., in a house, in a room ina building, in a sickroom or operating room in a hospital, in a car, inan aircraft, in a ship, in a storehouse, or in a compartment in arefrigerator).

BACKGROUND ART

In general, in an air-tight, ill-ventilated room such as an office roomor meeting room, the presence of a large number of people in itincreases the amounts of air pollutants such as carbon dioxide—which thepeople breathe out—, cigarette smoke, and dust. This reduces thequantity of negative ions—which have the effect of relaxinghumans—present in the air. In particular, the presence of cigarettesmoke may reduce the quantity of negative ions to about ½ to ⅕ of theirnormal quantity. To cope with this, various ion generating apparatusesthat are designed to replenish the air with negative ions haveconventionally been commercially available.

However, conventional ion generating apparatuses exploiting electricdischarge are typically of the type that generates negative ions by theuse of a high negative direct-current voltage, and are aimed atappealing to consumers with a relaxing effect. Accordingly, such iongenerating apparatuses can simply replenish the air with negative ions,but cannot actively remove airborne bacteria and the like floating inthe air.

Here are the results of our searching the past patent publications froexamples of other types of ion generating apparatuses.

Japanese Patent Application Laid-Open No. H4-90428 (hereinafter referredto as Patent Publication 1) describes an ion generator wherein a highalternating-current voltage is applied to a discharge wire or adischarge plate having an acute-angled corner to generate negative ionsalone or both negative and positive ions. This publication, however,only makes mention of a high alternating-current voltage unit as to themethod or means of generating ions. Here, the assumed area ofapplication is air conditioners, and the asserted effects are comfortand relaxation to humans.

Japanese Patent Application Laid-Open No. H8-217412 (hereinafterreferred to as Patent Publication 2) describes a corona discharger thathas a pair of electrodes, namely a discharge electrode and an inductionelectrode, arranged so as to sandwich an insulating member and that isprovided with a high-voltage power supply for feeding a highalternating-current voltage between those electrodes. This publicationdescribes the high-voltage power supply as having a diode connectedbetween the electrodes so that, according to the direction in which thediode points, either a negative potential or a positive potential ischosen as the supplied voltage. However, this publication makes nomention of how such switching is achieved. Here, the assumed area ofapplication is corona discharge equipment such as ozone generatingapparatuses, charging apparatuses, and ion generating apparatuses. Theasserted effect is generation of ions.

Japanese Patent Application Laid-Open No. H3-230499 (hereinafterreferred to as Patent Publication 3) describes an ion generatingapparatus wherein a large number of pairs of electrodes—each pairconsisting of a needle-shaped discharge electrode and an conductivegrounding grid or ring—arranged two-dimensionally across the stream ofpurified air, and wherein a negatively biased high sinusoidalalternating-current voltage is applied to some of the dischargeelectrodes and a positively biased high sinusoidal alternating-currentvoltage is applied to some other of the discharge electrodes so that, ofthe plurality of pairs of electrodes, some release positive ions andsome other release negative ions. This ion generating apparatus includesa means for controlling the bias voltage, and this permits adjustment ofthe quantities of positive and negative ions. The assumed area ofapplication is charge neutralizing equipment for clean rooms, and theasserted effect is neutralization of electric charges.

Japanese Patent Application Laid-Open No. H9-610 (hereinafter referredto as Patent Publication 4) describes a dust collecting apparatuswherein the voltages applied to electrodes at which to cause positiveand negative electric discharge are variable. The electrodes are anionizing wire and a dust collecting plate, which are designed to chargedust and thereby collect it in on the dust collecting plate. The assumedarea of application is electric dust collecting apparatuses for airconditioning equipment, and the asserted effect is sterilization of theinterior of such apparatuses by the action of the ozone generated byelectric discharge.

Ion generating electrodes exploiting electric discharge divide roughlyinto two types. One type is, as described in Patent Publications 1, 3,and 4, a metal wire, a metal plate having an acute-angled corner, or aneedle combined with, as an opposite electrode, the earth or a metalplate or a grid kept at the grounded potential, with air serving as aninsulating member. The other type is, as described in Patent Publication2, Japanese Patent Application Laid-Open No. 2003-47651 (hereinafterreferred to as Patent Publication 5), and Japanese Patent ApplicationLaid-Open No. 2002-319472 (hereinafter referred to as Patent Publication6)—of which the latter two will be described later—, a combination of adischarge electrode and an induction electrode formed with a soliddielectric member sandwiched in between. The former is characterized inthat the use of air as an insulating member permits the electrodes to bekept farther away from each other than in the latter and thus requires ahigher voltage to cause electric discharge. By contrast, the latter ischaracterized in that the use of an insulating member having a highinsulation resistance and a high dielectric constant permits thedistance between the electrodes to be made smaller (narrower) and thusrequires a lower application voltage than in the former.

There have conventionally been made inventions relating to iongenerating apparatuses (for example, see Patent Publications 5 and 6)that exploit the effects produced by releasing ions of oppositepolarities, i.e., positive and negative ions. These ion generatingapparatuses generate and release into the air approximately equalquantities of H⁺(H₂O)_(m) as positive ions and O₂ ⁻(H₂O)_(n) as negativeions (where m and n are natural numbers) so that those ions surroundairborne mold spores and viruses floating in the air and deactivate themby the action of a free radical, namely hydroxyl radical (.OH),generated as a result.

These inventions have already been put into practical use by theapplicant of the present application. The actual products are iongenerating apparatuses composed of a ceramic dielectric member, adischarge electrode arranged outside the dielectric member, and aninduction electrode arranged inside the dielectric member, and airpurifiers and air conditioners incorporating such ion generatingapparatuses.

Negative ions are believed to produce the following effects. In a spacein a household where an excessive quantity of positive ions are presentdue to electric appliances or for other causes, releasing a largequantity of negative ions helps to restore a state in whichwell-balanced quantities of positive and negative ions are present as ina wild forest, and to obtain a relaxing effect. Patent Publication 1makes mention of such a relaxation effect.

DISCLOSURE OF THE INVENTION

An object of the present invention is to generate positive and negativeions for the purpose of deactivating mold spores and viruses floating inthe air, and to achieve that more effectively. In general, iongenerating apparatuses exploiting electric discharge generate ozone atthe same time that they generate ions. Patent Publication 4 describeshow the oxidizing ability of ozone is used to achieve sterilizationinside apparatuses. It is generally known that a high concentration ofozone is hazardous to the human body. Thus, for the applicant of thepresent application, it is a highly difficult object to maximize thequantity of ions while minimizing the amount of ozone generated.

The applicant of the present application has applied for patents for iongenerating apparatuses as described in Patent Publications 5 and 6 etc.in the field of small-size ion generating apparatuses that can beincorporated not in equipment as targeted by Patent Publication 3 but inelectric appliances for household use. By the use of those iongenerating apparatuses, it is possible to generate approximately equalquantities of positive and negative ions.

To alleviate the neutralization of simultaneously generated positive andnegative ions among themselves, it is common to spread the ions into aspace by carrying them on a wind stream. However, where positive andnegative ions are generated simultaneously, it is inevitable that partof the ions of opposite polarities neutralize and vanish as soon as theyare generated. In the ion generating apparatus described in PatentPublication 3, a large number of electrodes are arrangedtwo-dimensionally across the stream of purified air. That is, the windstream flows in the direction in which needle extend. For compactness,safety, and energy saving, the applicant of the present applicationgives priority to reducing the applied voltage, and thus adopts astructure in which a pair of electrodes is formed by a dischargeelectrode formed on the surface of a dielectric member and an inductionelectrode buried in the dielectric member. In this case, a wind streamflowing in the direction described in Patent Publication 3 mentionedabove is not suitable to spread ions, and therefore a wind stream isblown parallel to the surface of the dielectric member. When a developedion generator is incorporated in various products, it is effective tolimit the direction of the wind stream blown to the ion generator to theideal direction, but there may be cases where such limitation isimpossible.

An object of the present invention is to provide an ion generatingelement and an ion generating apparatus that are so designed as toalleviate the neutralization among the generated ions themselves toachieve effective releasing of ions and that thus operate with enhancedion generation efficiency. Another object of the present invention isprovide an electric appliance incorporating such an ion generatingelement or apparatus.

To achieve the above object irrespective of whether a wind stream isblown from the X- or Y-axis direction with respect to a base member,according to the present invention, in an ion generating elementprovided with at least one first discharger for generating positive ionsand at least one second discharger for generating negative ions, bothfitted or printed on a single base member, the first and seconddischargers are arranged both on the same flat surface of the basemember but separately from and independently of each other on a diagonalline of the flat surface (i.e., obliquely). Here, the electrodes may beneedle-shaped electrodes, but, basically, the applicant of the presentapplication assumes the use of a pair of electrodes consisting of adischarge electrode formed on the surface of a dielectric member and aninduction electrode buried in the dielectric member. Here, to preventthe ions generated at the windward-side discharger from beingneutralized at the leeward-side discharger of the opposite polarityirrespective of whether the wind stream is blown from the X- or Y-axisdirection with respect to the surface of the discharge electrode on thedielectric member, the first and second dischargers are arranged on adiagonal line, i.e., obliquely, with respect to the direction of thewind stream (in the X- or Y-axis direction).

In a case where there are restrictions on the area on the base member onwhich the first and second dischargers can be fitted or printed,securing an insulating distance between the first and second dischargersmay make it difficult to arrange them on a diagonal line (i.e.,obliquely) as described above. In that case, a first conducting portionis arranged so as to surround the perimeter or a part of a firstdischarging portion—which generates positive ions—and is kept at anequal potential with the first discharging portion. The seconddischarger—which generates negative ions—is structured in a similarmanner. The first and second conducting portions are arranged on thesame flat surface but separately from and independently of each other insuch a way that they face each other. The positive ions released fromthe first discharging portion, before they are neutralized by theopposite potential at the second discharging portion, are repelled bythe first conducting portion—surrounding the first discharging portionand kept at an equal potential therewith—and are released together withthe wind stream. The same is true with the second discharging portion.Here, as described above, the electrodes may be needle-shapedelectrodes, but, basically, they are assumed to be a pair of electrodesconsisting of a discharge electrode formed on the surface of adielectric member and an induction electrode buried in the dielectricmember.

According to the present invention, in an ion generating elementprovided with at least one first discharger for generating positive ionsand at least one second discharger for generating negative ions, bothfitted or printed on a single base member, the first and seconddischargers are each composed of a pair of a first or second dischargingelectrode, respectively, formed on the surface of a dielectric memberserving as the base member and a first or second induction electrode,respectively, buried in the dielectric member, and are arranged both onthe same flat surface of the base member but separately from andindependently of each other. This construction can alleviate theneutralization of the generated ions among themselves as compared withone in which positive and negative ions are generated alternately atpredetermined time intervals by the use of a single ion generatingelement.

By arranging the first and second dischargers in such a way that thefirst and second discharge electrodes are located at a predetermineddistance from each other, it is possible to prevent occurrence of sparks(spark discharge) between the first and second discharge electrodes andthereby enhance reliability. It is also possible to further alleviatethe neutralization among the generated ions themselves.

In a construction in which a pair of electrodes is used that consists ofa discharge electrode formed on the surface of a dielectric member andan induction electrode buried in the dielectric member, from theperspective of reducing the generation of ozone, the waveform of thevoltage applied to the first and second dischargers is not a commonsinusoidal alternating-current waveform as disclosed in PatentPublications 2 and 3. Instead, in an ion generating element according tothe invention, an alternating-current impulse voltage is applied. Thishelps to generate ions stably and to keep ozone low. A voltage waveformobtained by positively biasing an alternating-current impulse voltage isapplied to the first discharger to generate positive ions, and a voltagewaveform obtained by negatively biasing the same alternating-currentimpulse voltage is applied to the second discharger to generate negativeions.

The voltage application circuit is provided with a first voltageapplication portion and a switching portion whose operation can beswitched between a mode in which they generate positive ions by applyingto the first discharger of the ion generating element a voltage waveformobtained by positively biasing an alternating-current impulse voltageand a mode in which they generate negative ions by applying to the firstdischarger of the ion generating element a voltage waveform obtained bynegatively biasing the same alternating-current impulse voltage, and asecond voltage application portion that generates negative ions byapplying to the second discharger of the ion generating element avoltage waveform obtained by negatively biasing the samealternating-current impulse voltage. This makes it possible to switchthe operation between a mode in which both positive and negative ionsare generated and a mode in which only negative ions are generated.Thus, it is possible to switch the polarity of the generated ionsautomatically or manually according to the environment, situation, orpurpose in or for which the ion generating apparatus is used. When bothpositive and negative ions are generated, the purpose is to deactivatemold spores and viruses floating in the air. When only negative ions aregenerated, the purpose is to bring a state in which an excessivequantity of positive ions are present due to electric appliances or forother causes in a household back to a state in which well-balancedquantities of positive and negative ions are present, or to obtain arelaxing effect. Such switching is possible by the use of a singleelectrode and a single ion generating apparatus.

To realize the above-described switching at low cost and with a smallnumber of components, the voltage application circuit is provided with athird voltage application portion and a bias switching portion whoseoperation can be switched between a mode in which they generate positiveions by applying to the first discharger of the ion generating element avoltage waveform obtained by positively biasing an alternating-currentimpulse voltage and a mode in which they generate positive and negativeions by applying to the first discharger of the ion generating element anon-biased alternating voltage waveform of the same alternating-currentimpulse voltage, and a second voltage application portion that generatesnegative ions by applying to the second discharger of the ion generatingelement a voltage waveform obtained by negatively biasing the samealternating-current impulse voltage. This makes it possible to switchoperation between a mode in which approximately equal quantities ofpositive and negative ions are generated and a mode in which a largequantity of negative ions relative to the quantity of positive ions aregenerated. Thus, it is possible to switch the polarity of the generatedions automatically or manually according to the environment, situation,or purpose in or for which the ion generating apparatus is used. Whenapproximately equal quantities of ions are generated, the purpose is todeactivate mold spores and viruses floating in the air. When a largerquantity of negative ions are generated, the purpose is to bring a statein which an excessive quantity of positive ions are present due toelectric appliances or for other causes in a household back to a statein which well-balanced quantities of positive and negative ions arepresent, or to obtain a relaxing effect. Such switching is possible bythe use of a single ion generating apparatus.

Advisably, the alternating-current impulse voltage applied to the firstdischarger is an alternating voltage waveform such that the voltage atthe first induction electrode relative to the first dischargingelectrode starts with a positive polarity, and the alternating-currentimpulse voltage applied to the second discharger is an alternatingvoltage waveform such that the voltage at the second induction electroderelative to the second discharging electrode starts with a negativepolarity. In other words, the crest level of the first wave of thevoltage at the first induction electrode relative to the first dischargevoltage is made higher to the positive polarity side, and the crestlevel of the first wave of the voltage at the second induction electroderelative to the second discharge voltage is made higher to the negativepolarity side.

The voltage application circuit includes a first diode that has thecathode thereof connected to a reference potential (=grounded potential,described later in connection with embodiments) and has the anodethereof connected to the second discharging electrode, and a seconddiode that has the anode thereof connected to the reference potentialand has the cathode thereof connected to the first dischargingelectrode. By permitting the choice of whether or not to connect thesecond diode to the reference voltage, whereas the alternating-currentimpulse voltage applied to the second discharge electrode is negativelybiased, it is possible to choose whether the alternating-current impulsevoltage applied to the first discharge electrode is positively biased ora non-biased alternating voltage waveform is applied thereto.

Advisably, the voltage application circuit includes a first diode thathas the cathode thereof connected to a reference potential and has theanode thereof connected to the second discharging electrode, a seconddiode that, when the first discharger generates positive ions, has theanode thereof connected to the reference potential and has the cathodethereof connected to the first discharging electrode, and a third diodethat, when the first discharger generates negative ions, has the cathodethereof connected to the reference potential and has the anode thereofconnected to the first discharging electrode. Thus, whereas thealternating-current impulse voltage applied to the second dischargeelectrode is negatively biased, the alternating-current impulse voltageapplied to the first discharge electrode is positively or negativelybiased.

Advisably, the voltage application circuit includes a first transformerhaving a primary coil that is driven, a first secondary coil from whichthe alternating-current impulse voltage is applied to the firstdischarger, and a second secondary coil from which thealternating-current impulse voltage is applied to the second discharger,and the first and second secondary coils of the first transformer arearranged on both sides of the primary coil. This makes it possible tosecure a distance between the first and second secondary coils, and thusto alleviate the direct influence of the magnetic field generated by oneof the secondary coils on the other.

Advisably, the voltage application circuit includes a second transformerhaving a primary coil that is driven and a secondary coil from which thealternating-current impulse voltage is applied to the first dischargerand a third transformer having a primary coil that is driven and asecondary coil from which the alternating-current impulse voltage isapplied to the second discharger, and the secondary coil of the secondtransformer, the primary coil of the second transformer, the primarycoil of the third transformer, and the secondary coil of the thirdtransformer are arranged in this order. This makes it possible to securea distance between the secondary coils of the second and thirdtransformers, and thus to alleviate the direct influence of the magneticfield generated by one of the secondary coils on the other.

The primary coil of the second transformer and the primary coil of thethird transformer may be connected in parallel. This makes the voltagesapplied to the first coils of the second and third transformers equal.Thus, by giving the second and third transformers the samecharacteristics, it is possible to make equal the absolute values of thealternating-current impulse voltages applied to the first and seconddischargers.

The primary coil of the second transformer and the primary coil of thethird transformer may be connected in series. This makes the currentsflowing through the first coils of the second and third transformersequal. Thus, by giving the second and third transformers the samecharacteristics, it is possible to make equal the absolute values of thealternating-current impulse voltages applied to the first and seconddischargers.

A flywheel diode may be connected to each of the primary coils of thesecond and third transformers. Then, the current that is produced by thevoltage induced in the primary coil of the second transformer by thecurrent flowing through the secondary coil of the second transformerflows back through the primary coil of the second transformer andthrough the flywheel diode connected thereto, and thus no longerinfluences the third transformer. Likewise, the current that is producedby the voltage induced in the primary coil of the third transformer bythe current flowing through the secondary coil of the third transformerflows back through the primary coil of the third transformer and throughthe flywheel diode connected thereto, and thus no longer influences thesecond transformer. Accordingly, if a load variation or the like occursin one of the dischargers, the variation does not influence the voltageapplied to the other discharger, and thus the quantity of ions generatedby the other discharger is prevented from varying.

In the ion generating elements constructed as described above, thedischarge electrode contacts and the induction electrode contacts viawhich the predetermined voltage waveforms are applied to the dischargeelectrodes and the induction electrodes of the first and seconddischargers are arranged also on the surface of the dielectric memberbut on the face opposite to the face on which the discharge electrodesare arranged so as not to hamper electric discharge and generation ofions. The number of contacts provided for the first and seconddischargers is four in total. The contacts are so arranged that thecontact for the first discharge electrode and the contact for the seconddischarge electrode between which the potential difference is lowest arelocated adjacent to and at a predetermined distance from each other.This helps obtain further enhance reliability.

Likewise, the first and second dischargers are arranged on the basemember in such a way that the first discharge electrode and the seconddischarge electrode between which the potential difference is lowest arelocated at a predetermined distance from each other. This helps obtainfurther enhance reliability.

According to the present invention, an electric appliance is provided,advisably, with one of the ion generating apparatuses constructed asdescribed above and a releaser (such as a fan) for releasing the ionsgenerated by the ion generating apparatus. With this construction, it ispossible to achieve, in addition to the functions of the electricappliance itself, the function of varying the quantity and balance ofions in the air by operating the incorporated ion generating apparatusand thereby produce a desired environment in a room.

The electric appliance constructed as described above generatesH⁺(H₂O)_(m) as positive ions and O₂ ⁻(H₂O)_(n) as negative ions (where mand n are natural numbers, and denote accompaniment by a plurality ofH₂O molecules). By generating approximately equal quantities ofH⁺(H₂O)_(m) and O₂ ⁻(H₂O)_(n) in the air in this way, it is possible tomake the two types of ions attach to airborne bacteria and the likefloating in the air and deactivate them by the action of a free radical,namely hydroxyl radical (.OH), generated as a result.

BRIEF DESCRIPTION OF DRAWINGS

FIGS. 1A to 1H are schematic diagrams showing examples of basicexperiments of the independent ion release method according to theinvention;

FIGS. 2A and 2B are schematic diagrams showing a first embodiment of anion generating apparatus according to the invention;

FIG. 3 is a schematic diagram showing a second embodiment of an iongenerating apparatus according to the invention;

FIGS. 4A and 4B are schematic diagrams showing a third embodiment of anion generating apparatus according to the invention;

FIGS. 5A to 5G are circuit diagrams and voltage waveform diagramsshowing an embodiment of the voltage application circuit;

FIGS. 6A to 6D are schematic diagrams showing other examples of basicexperiments of the independent ion release method according to theinvention;

FIG. 7 is a diagram showing the results of other examples of basicexperiments of the independent ion release method according to theinvention;

FIG. 8 is a schematic diagram showing a fifth embodiment of an iongenerating apparatus according to the invention;

FIG. 9 is a schematic diagram showing a sixth embodiment of an iongenerating apparatus according to the invention;

FIG. 10 is a schematic diagram showing a seventh embodiment of an iongenerating apparatus according to the invention;

FIG. 11 is a schematic diagram showing an eighth embodiment of an iongenerating apparatus according to the invention;

FIG. 12 is a circuit diagram showing another embodiment of the voltageapplication circuit;

FIG. 13 is a circuit diagram showing still another embodiment of thevoltage application circuit;

FIGS. 14A and 14B are waveform diagrams showing operation voltagewaveforms of the voltage application circuit shown in FIGS. 12 and 13;

FIGS. 15A and 15B are waveform diagrams showing other operation voltagewaveforms of the voltage application circuit shown in FIGS. 12 and 13;

FIGS. 16A and 16B are waveform diagrams showing other operation voltagewaveforms of the voltage application circuit shown in FIGS. 12 and 13;

FIGS. 17A and 17B are waveform diagrams showing other operation voltagewaveforms of the voltage application circuit shown in FIGS. 12 and 13;

FIGS. 18A and 18B are waveform diagrams showing other operation voltagewaveforms of the voltage application circuit shown in FIGS. 12 and 13;

FIG. 19 is a diagram showing the arrangement of components in an iongenerating apparatus incorporating the transformer shown in FIG. 12; and

FIG. 20 is a diagram showing the arrangement of components in an iongenerating apparatus incorporating the transformer shown in FIG. 13.

BEST MODE FOR CARRYING OUT THE INVENTION

In an ion generating apparatus according to the present invention, toalleviate the neutralization and vanishment of the generated positiveand negative ions near the electrodes of the ion generating element, andto effectively release the generated ions of opposite polarities into aspace, instead of a method of generating positive and negative ionsalternately at predetermined time intervals by the use of a single iongenerating element, a method of generating positive and negative ionsseparately by the use of a plurality of ion generating elements anddischarging them independently into a room (hereinafter referred to asthe independent ion release method) is adopted.

Prior to the adoption of the above-mentioned independent ion releasemethod, basic experiments were conducted as described below. The iongenerating element used in these experiments may employ needle-shapedelectrodes. Here, however, it is assumed that a construction is adoptedin which a pair of electrodes is formed by a discharge electrode formedon the surface of a dielectric member and an induction electrode buriedin the dielectric member.

FIGS. 1A to 1H are schematic diagrams showing examples of basicexperiments of the independent ion release method according to theinvention. FIG. 1A is an external view of the ion generating element,FIG. 1B is a sectional view of the ion generating element, FIG. 1C showsthe waveform of the voltage applied between the discharge and inductionelectrodes, and FIGS. 1D to 1G are diagrams showing differentmeasurement conditions, and FIG. 1H shows an example of the arrangementof the ion generating element.

In the experiments, first, on one hand, by the use of the ion generatingelement 1 shown in FIGS. 1A and 1B, an alternating-current impulsevoltage (FIG. 1C) was applied between the discharge electrode 0 a and aninduction electrode 0 b thereof so that positive and negative ions weregenerated alternately at predetermined time intervals (FIG. 1D), and, onthe other hand, by the use of the same ion generating element 1, anegatively-biased alternating-current impulse voltage was applied sothat only negative ions were generated (not illustrated). In each ofthese cases, the quantity of ions released was measured to find whetherthere were any differences between the two cases. As a result, it wasfound that the total quantity of positive and negative ions detected inthe former case was only about 50 to 60 [%] of the quantity of negativeions detected in the latter case.

Next, with the above results taken into consideration, two iongenerating elements 1 a and 1 b, of which each was the same as the oneused above, were arranged so that the two ion generating elementsgenerated only positive and negative ions, respectively, and the totalquantity of ions released was measured (FIGS. 1E to 1G).

As a result, it was found that the total quantity of positive andnegative ions obtained under the measurement conditions shown in FIG. 1Ewas approximately equal to the sum of the quantities of positive andnegative ions measured separately by the use of two ion generatingelements as described above. This indicates that an ion generatingelement adopting the independent ion release method is more effectivethan one adopting the method of generating positive and negative ionsalternately at predetermined time intervals by the use of a single iongenerating element.

It should be noted that, In FIG. 1E, the arrangement of a firstdischarger (ion generating element 1 a) and a second discharger (iongenerating element 1 b) is perpendicular to the wind stream from the fan2, and thus the air stream that passes above one ion generating elementnever passes over the other.

On the other hand, in FIGS. 1F and 1G, where the arrangement is 90degrees changed from FIG. 1E, i.e., where the arrangement of the iongenerating elements 1 a and 1 b is parallel to the wind stream from thefan 2, it has been confirmed that the quantity of ions generated by thewindward-side discharger diminishes. Specifically, in FIG. 1F, thepositive ions generated by the windward-side ion generating element 1 apasses above the leeward-side ion generating element 1 b, and thus thosepositive ions are neutralized by the negative potential at the iongenerating element 1 b, resulting in a diminished quantity of positiveions. Likewise, in FIG. 1G, the negative ions generated by thewindward-side ion generating element 1 b diminishes. This indicatesthat, even when the independent ion release method is adopted, dependingon the arrangement of the dischargers, ions may not be releasedeffectively, resulting in a diminished quantity of ions of one type andthus ill-balanced quantities of positive and negative ions released.

Here, ions are measured by the use of an ion counter 3 that adopts theGerdien double cylinder method, and the measured values areconcentrations [ions/cc] at measurement points. The magnitude of the ionconcentration obtained under the same conductions and at the samemeasurement point is measured, and therefore, in the presentspecification, a high or low ion concentration is referred to as thequantity of ions being large or small, respectively.

In a case where an ion generating apparatus is incorporated in anappliance, irrespective of whether the appliance blows a wind stream tothe surface of the discharge electrodes on the dielectric member fromthe X- or Y-axis direction, to prevent the ions generated by thewindward-side discharger from being neutralized on the leeward-sidedischarger of the opposite polarity, it is preferable, to alleviateneutralization, that the ion generating elements 1 a and 1 b be arrangedon a diagonal line, i.e., obliquely, with respect to the X- or Y-axisdirection (see FIG. 1H). This, however, is disadvantageous from theviewpoint of the area occupied, and therefore, in a case where thedirection of the wind stream is fixed, it is preferable not to adopt adiagonal arrangement.

Also conducted were basic experiments for finding the relationshipbetween the distance between the discharge electrode that generatespositive ions and the discharge electrode that generates negative ionsand the quantities of ions neutralized among the ions of the two typesgenerated. FIGS. 6A to 6D are schematic diagrams showing other examplesof basic experiments of the independent ion release method according tothe invention. FIG. 6A is a diagram showing the arrangement ofelectrodes on the obverse face of an film electrode, FIG. B is a diagramshowing the arrangement of electrodes on the reverse face of the filmelectrode, FIG. 6C is a diagram showing the waveform of the voltageapplied between the discharge and induction electrodes, and FIG. 6D is adiagram showing the measurement conditions.

In FIGS. 6A to 6D, reference numeral 60 represents a film electrodehaving two electrodes formed on each of its obverse and reverse faces byprinting and then etching copper on a polyimide film. On the obverseface, as shown in FIG. 6A, there are formed discharge electrodes 61 aand 62 a, each a substantially rectangular grid-patterned electrode,with a discharge electrode interval d left in between. On the reverseface, as shown in FIG. 6B, there are formed induction electrodes 61 band 62 b, each a substantially rectangular solid plate electrode, inpositions opposite to the discharge electrodes 61 a and 62 a. To preventabnormal discharge at the edges of the discharge electrodes 61 a and 62a, the induction electrodes 61 b and 62 b are formed smaller than andinside the discharge electrodes 61 a and 62 a.

The solid black circles shown on the electrodes are solder pads 63, and,via leads or the like soldered thereto, a high voltage is applied to theelectrodes to generate ions. Between the discharge electrode 61 a andthe induction electrode 61 b is applied an alternating-current impulsevoltage having an alternating and gradually decreasing waveform as shownin FIG. 6C after being positive biased. Between the discharge electrode62 a and the induction electrode 62 b is applied the samealternating-current impulse voltage after being negatively biased. As aresult, positive ions are generated from the discharge electrode 61 a,and negative ions are generated from the discharge electrode 62 b. Thecrest level of the first wave of the applied alternating-current impulsevoltage is about 3 kV.

A plurality of film electrodes 60 were produced with varying dischargeelectrode intervals d, and, with each of those film electrodes 60, asshown in FIG. 6D, the film electrode 60 was placed between the fan 2 andthe ion counter 3, and the concentration of ions generated when thewaveform obtained by positively or negatively biasing theabove-mentioned altemating-current impulse voltage was applied weremeasured separately for positive and negative ions. Measurements weremade separately in the case where only positive ions were generated, inthe case where only negative ions were generated, and in the case inwhich both positive and negative ions were generated simultaneously.Here, the distance from the ion generating element 60 to the ion counter3 was 25 cm, both placed 4.5 cm above the measurement table.

FIG. 7 shows the measurement results. When the measurements were made,the temperature was 27° C., and the humidity was 27%. These results showthat, when the discharge electrode interval d is 5 mm or more, no spark(spark discharge) occurs between the discharge electrodes 61 a and 62 a.Moreover, when the discharge electrode interval d was 8 mm, thequantities of positive and negative ions were equal between when onlypositive or negative ions were generated and when both positive andnegative ions were generated. This indicates that, under the conditionsof the film electrodes used in the measurements, a discharge electrodeinterval d of 8 mm or more prevents the neutralization among thepositive and negative ions generated. A larger discharge electrodeinterval d is more advantageous to preventing sparks and preventing theneutralization among ions of opposite polarities. However, increasing itresults in increasing the size of the ion generating element.Accordingly, under the conditions described above, it is advisable toset the discharge electrode interval d at about 8 mm. It should be notedthat, in these measurements, when samples of film electrodes withvarying discharge electrode intervals d were produced, the dischargeelectrode interval d was secured by etching. Accordingly, in thisportion, the coating layer that coats the surface of the electrodes wasnot present, and thus copper was exposed in parts of the edges at whichthe discharge electrodes faced each other. By contrast, in the actualelectrodes described below, the presence of the coating layer isexpected to permit the discharge electrode interval d to be madesmaller.

From the results of the basic experiments described above, it is nowclear that it is preferable to alleviate neutralization by arranging theion generating elements 1 a and 1 b on a diagonal line, i.e., obliquely,as shown in FIG. 1H. This (a diagonal arrangement) is realized in afirst embodiment of the invention shown in FIGS. 2A and 2B. FIGS. 2A and2B are diagrams schematically showing the construction of a firstembodiment of an ion generating apparatus according to the invention.FIGS. 2A and 2B schematically show a plan view and a side view,respectively, of the ion generating apparatus.

As shown in FIGS. 2A and 2B, an ion generating apparatus according tothe invention comprises an ion generating element 10 that is providedwith a plurality of (in this embodiment, two) dischargers for generatingions and a voltage application circuit 20 that applies a predeterminedvoltage to the ion generating element 10.

The ion generating element 10 comprises a dielectric member 11 (an upperdielectric member 11 a and a lower dielectric member 11 b), a firstdischarger 12 (a discharge electrode 12 a, an induction electrode 12 b,a discharge electrode contact 12 c, an induction electrode contact 12 d,connection terminals 12 e and 12 f, and connection paths 12 g and 12 h),a second discharger 13 (a discharge electrode 13 a, an inductionelectrode 13 b, a discharge electrode contact 13 c, an inductionelectrode contact 13 d, connection terminals 13 e and 13 f, andconnection paths 13 g and 13 h), and a coating layer 14. As will bedescribed later, by applying a voltage between the first dischargeelectrode 12 a and the first induction electrode 12 b and anotherbetween the second discharge electrode 13 a and the second inductionelectrode 13 b, electric discharge is caused near the dischargeelectrodes 12 a and 13 a so as to generate positive and negative ions,respectively.

The dielectric member 11 (for example, 15 [mm] long, 37 [mm] wide, and0.45 [mm] thick) is formed by bonding together the upper and lowerdielectric members 11 a and 11 b, each having substantially the shape ofa rectangular parallelepiped. In a case where the dielectric member 11is formed of an inorganic material, it is formed of ceramic such ashigh-purity alumina, crystallized glass, forsterite, or steatite. In acase where the dielectric member 11 is formed of an organic material, itis formed of resin such as polyimide or glass epoxy that is highlyresistant to oxidation. From the viewpoint of resistance to corrosion,it is preferable to use an inorganic material as the material of thedielectric member 11, and, from the viewpoint of formability and offacility of electrode formation, which will be described later, it ispreferable to use ceramic.

It is desirable that the insulation resistance between the dischargeelectrodes 12 a and 13 a and the induction electrodes 12 b and 13 b beuniform, and therefore it is preferable to use as the material of thedielectric member 11 one whose density does not vary much and whoseinsulation factor is uniform.

The dielectric member 11 may be given any other shape than substantiallythe shape of a rectangular parallelepiped (for example, the shape of acircular or elliptic plate, or the shape of a polygonal plate), and mayeven be given a cylindrical shape. From the viewpoint of productivity,however, it is preferable to give it the shape of a flat plate(including the shapes of a circular plate and of a rectangularparallelepiped).

The first and second dischargers 12 and 13 are arranged on a diagonalline (obliquely) with respect to the shape of the dielectric member 11so as not to be located on a straight line. More functionally defined,the arrangement of the first and second dischargers 12 and 13 is suchthat, no matter from which direction an air stream may be blown to theion generating element 10 of this embodiment, the direction of theirarrangement is perpendicular to the air stream, in other words, suchthat the air stream that has passed above one discharger does not passabove the other discharger. With this construction, it is possible tomake the most of the independent ion release method, and to alleviatethe reduction of the ions generated by the two dischargers 12 and 13 andthereby achieve efficient and well-balanced release of ions.

The discharge electrodes 12 a and 13 b are formed on the surface of theupper dielectric member 11 a integrally therewith. The dischargeelectrodes 12 a and 13 a may be formed of any material such as tungstenthat is electrically conductive, provided that the material is notdeformed as by being melted by electric discharge.

The induction electrodes 12 b and 13 b are arranged parallel to thedischarge electrodes 12 a and 13 a with the upper dielectric member 11 asandwiched in between. This arrangement permits the distance between thedischarge electrodes 12 a and 13 a and the induction electrodes 12 b and13 b (hereinafter referred to as the interelectrode distance) fixed.Thus, it is possible to uniformize the insulation resistance betweenthose electrodes, thereby to stabilize the state of electric discharge,and thus to generate positive and/or negative ions appropriately. Itshould be noted that, in a case where the dielectric member 11 is givena cylindrical shape, it is possible to keep the above-mentionedinterelectrode distance fixed by forming the discharge electrodes 12 aand 13 a on the outer circumferential surface of the cylinder andforming the induction electrodes 12 b and 13 b in the shape of a shaft.

The induction electrodes 12 b and 13 b, like the discharge electrodes 12a and 13 a, may be formed of any material such as tungsten that iselectrically conductive, provided that the material is not deformed asby being melted by electric discharge.

The discharge electrode contacts 12 c and 13 c electrically conduct tothe discharge electrodes 12 a and 13 a via the connection terminals 12 eand 13 e and the connection paths 12 g and 13 g formed on the sameformation surface as the discharge electrodes 12 a and 13 a (i.e., onthe surface of the upper dielectric member 11 a). Accordingly, byconnecting one ends of leads (copper or aluminum leads) to the dischargeelectrode contacts 12 c and 13 c, and then connecting the other ends ofthose leads to the voltage application circuit 20, it is possible tomake the discharge electrodes 12 a and 13 a electrically conduct to thevoltage application circuit 20.

The induction electrode contacts 12 d and 13 d electrically conduct tothe induction electrodes 12 b and 13 b via the connection terminals 12 fand 13 f and the connection paths 12 h and 13 h formed on the sameformation surface as the induction electrodes 12 b and 13 b (i.e., onthe surface of the lower dielectric member 11 b). Accordingly, byconnecting one ends of leads (copper or aluminum leads) to the inductionelectrode contacts 12 d and 13 d, and then connecting the other ends ofthose leads to the voltage application circuit 20, it is possible tomake the induction electrodes 12 b and 13 b electrically conduct to thevoltage application circuit 20.

It is preferable that the discharge electrode contacts 12 c and 13 c andthe induction electrode contacts 12 d and 13 d be all formed on thesurface of the dielectric member 11 but on a face other than the one(hereinafter referred to as the top face of the dielectric member 11) onwhich the discharge electrodes 12 a and 13 a are formed. With thisconstruction, no unnecessary leads are arranged on the top face of thedielectric member 11, and thus the air stream from the fan (notillustrated) is less likely to be disturbed. This makes it possible toobtain the effects of the independent ion release method according tothe invention to the full.

Out of the above considerations, in the ion generating element 10 ofthis embodiment, the discharge electrode contacts 12 c and 13 c and theinduction electrode contacts 12 d and 13 d are all formed on the face(hereinafter referred to as the bottom face of the dielectric member 11)of the dielectric member 11 opposite to the top face thereof.

It should be noted that, in the ion generating element 10 of thisembodiment, the first discharge electrode 12 a and the second dischargeelectrode 13 a have acute-angled corners so that the electric fieldconcentrates there to cause localized electric discharge. Needless tosay, it is possible to use any other pattern than specifically shown inthe figures so long as it can concentrate the electric field. The sameis true with FIGS. 3, 4A, and 4B.

FIG. 3 is a schematic plan view showing a second embodiment of an iongenerating apparatus according to the invention. The structure as seenin a sectional view is largely the same as that shown in FIG. 2B. Theembodiment shown in FIG. 3 is one in which, due to restrictions on theavailable area, the first and second discharging portions are notarranged on a diagonal line with respect to the shape of the dielectricmember 11 serving as the base member.

The first discharge electrode 12 a divides into a first dischargingportion 12 j for causing concentration of the electric field and therebycausing electric discharge, a first conducting portion 12 k surroundingthe perimeter or a part thereof, and the connection terminal 12 ementioned earlier. All these portions are formed in a single pattern, sothat the voltages applied thereto are equal. Likewise, the seconddischarge electrode 13 a divides into a second discharging portion 13 j,a second conducting portion 13 k, and the connection terminal 12 ementioned earlier.

Positive ions are generated at the first discharging portion 12 j, whichis at a positive potential. Right next thereto is located the seconddischarging portion 13 j, which is at a negative potential.

The distinctive feature here is that the first and second conductingportions 12 k and 13 k are so arranged as to surround the perimeters orparts of the first and second discharge portions 12 ja and 13 j, whichcause electric discharge. As a result of the first conducting portion 12k, which is at the same voltage as the first discharging portion 12 j,being arranged to surround the perimeter or a part of the firstdischarging portion 12 j, the positive ions generated from the firstdischarging portion 12 j are repelled by the first conducting portion 12k at a positive potential before reaching the second discharging portion13 j at the opposite polarity, i.e., at a negative potential. Thisalleviates the incidence of the positive ions reaching the seconddischarging portion 13 j. The same is true with the second conductingportion 13 k. It should be noted that, in a case where the direction ofthe air stream or the distance between the first and second dischargeelectrodes 12 a and 13 a is such that almost no neutralization occursamong the generated ions, there is no need to provide the first andsecond conducting portions 12 k and 13 k described above, through theseconstitute a characterizing feature.

FIGS. 4A and 4B are schematic plan views showing a third embodiment ofan ion generating apparatus according to the invention. The structure asseen in a sectional view is largely the same as that shown in FIG. 2B.The ion generating apparatus shown in FIGS. 4A and 4B has the samefeatures as the second embodiment described above, and in addition haselectrodes arranged on a diagonal line with respect to the shape of thedielectric member 11 serving as the base member as described earlier. Asdescribed earlier, the electrodes may be needle-shaped electrodes, but,basically, this embodiment assumes the use of a pair of electrodesconsisting of a discharge electrode formed on the surface of adielectric member and an induction electrode buried in the dielectricmember.

In a fourth embodiment of the invention, in the ion generatingapparatuses shown in FIGS. 2A, 2B, 3, 4A, and 4B, the first dischargeelectrode 12 a, the first induction electrode 12 b, the second dischargeelectrode 13 a, and the second induction electrode 13 b are arranged onthe dielectric member 11 in the following manner. The first and secondelectrodes are arranged next to each other not simply in such a way thatinsulation is secured between them, but further, with the appliedvoltage taken into consideration, in such a way that insulation issecured between the first discharge electrode 12 a and the seconddischarge electrode 13 a, i.e., those of all the electrodes betweenwhich the potential difference is the smallest. In other words, theelectrodes are arranged next to each other in such a way that insulationis secured between the combination of electrodes between which thepotential difference is smallest. The voltage differences and waveformswill be described later.

The shapes of the electrodes shown in FIGS. 2A, 3, 4A, and 4B are mereexamples, and the electrodes may be shaped as shown in FIGS. 8 to 11.FIGS. 8 to 11 are schematic plan views showing a fifth to an eighthembodiment, respectively, of ion generating apparatuses according to theinvention. In FIGS. 8 to 11, such components as are found also in FIG. 3are identified with the same reference numerals, and their explanationswill not be repeated. The structures as seen in a sectional view arelargely the same as that shown in FIG. 2B.

In the ion generating apparatus 10 shown in FIG. 8, the individualelectrodes are made so small that the first and second dischargeelectrodes 12 a and 13 a are not located too close to an edge. In theion generating apparatus 10 shown in FIG. 9, to permit adjustment of thedischarge spots, the number of first and second discharge electrodes 12a and 13 a are reduced as compared with their number in the iongenerating element 10 shown in FIG. 8. In the ion generating apparatuses10 shown in FIGS. 10 and 11, to permit adjustment of the dischargespots, the first and second discharge electrodes 12 a and 13 a of theion generating apparatus 10 shown in FIG. 9 are so modified as to haveshapes closer to the shapes of the first and second discharge electrodes12 a and 13 a of the ion generating apparatus 10 shown in FIG. 2.

Next, the configuration and operation of the voltage application circuit20 will be described.

FIGS. 5A and 5B are circuit diagrams showing embodiments of the voltageapplication circuit 20. First, the voltage application circuit 20 shownin FIG. 5A will be described. The voltage application circuit 20 shownin FIG. 5A comprises, as a primary-side drive circuit, an input powersource 201, an input resistor 204, a rectifying diode 206, a transformerdrive switching device 212, a capacitor 211, and a diode 207. In a casewhere the input power source 201 is commercially distributedalternating-current power, the voltage of the input power source 201charges the capacitor 211 through the input resistor 204 and therectifying diode 206. When the voltage here becomes higher than aprescribed voltage, the transformer drive switching device 212 turns onand applies the voltage to a primary coil 202 a of a transformer 202.Immediately thereafter, the energy accumulated in the capacitor 211 isdischarged through the primary coil 202 a of the transformer 202 and thetransformer drive switching device 212. This turns the voltage acrossthe capacitor 211 back to zero, and then charging starts again. In thisway, charging and discharging are repeated at prescribed time intervals.In the above description, the transformer drive switching device 212 isassumed to be a no-gate, two-terminal thyristor (a “Sidac” manufacturedby Shindengen Electric Manufacturing Co., Ltd., Japan). It is, however,also possible to adopt a slightly different circuit configuration usinga thyristor (SCR). The input power source 201 may be a direct-currentpower source so long as the circuit is so configured as to operate in asimilar way as described above. That is, the primary-side drive circuitof the circuit may be configured in any manner so long as it operates ina similar way.

The transformer 202 has, as a secondary-side circuit, two secondarycoils 202 b and 202 c, and these are connected respectively to the firstdischarge electrode 12 a, the first induction electrode 12 b, the seconddischarge electrode 13 a, and the second induction electrode 13 b shownin one of FIGS. 2A, 2B, 3, 4A, 4B, and 8 to 11. When the transformerdrive switching device 212 in the primary-side circuit turns on, theenergy on the primary side is transmitted to the secondary coils 202 band 202 c of the transformer, causing an impulse-shaped voltage toappear therein. To the first discharge electrode 12 a is connected notonly the secondary coil 202 b of the transformer 202 but also thecathode of a diode 209. The anode of the diode 209 is, through aresistor 205, grounded or connected to one side (the referencepotential) of the input power source 201. In a case where the inputpower source 201 is commercially distributed alternating-current power,since one side of the commercially distributed alternating-current inputpower is grounded in Japan, connecting an electric appliance or the likewithout a grounding terminal to one side of the input power source 201is equivalent to grounding it. Even if the plug is inserted in an outletin the wrong way, simply a voltage of 100 V is superimposed, and theelectric appliance or the like is grounded all the same. The resistor205 is for protection, and therefore omitting (or short-circuiting) itdoes not affect the operation in any way. To the second dischargeelectrode 13 a is connected not only the secondary coil 202 c of thetransformer but also the anode of a diode 208. The cathode of the diode208 is, through the resistor 205, grounded or connected to one side ofthe input power source 201.

Next, the differently configured voltage application circuit 20 shown inFIG. 5B will be described. The primary-side circuit of the transformer202 is the same as described above. The transformer 202 has, as asecondary-side circuit, two secondary coils 202 b and 202 c, and theseare connected respectively to the first discharge electrode 12 a, thefirst induction electrode 12 b, the second discharge electrode 13 a, andthe second induction electrode 13 b shown in one of FIGS. 2A, 2B, 3, 4A,4B, and 8 to 11. When the transformer drive switching device 212 in theprimary-side circuit turns on, the energy on the primary side istransmitted to the secondary coils 202 b and 202 c of the transformer,causing an impulse-shaped voltage to appear therein. To the firstdischarge electrode 12 a are connected not only the secondary coil 202 bof the transformer 202 but also the cathode of a diode 209 and the anodeof a diode 210. The anode of the diode 209 is connected to one selectionterminal 203 a of a switching relay 203, and the cathode of the diode210 is connected to another selection terminal 203 b of the switchingrelay 203. A common terminal 203 c of the switching relay 203 is,through a resistor 205, grounded or connected to one side of the inputpower source 201.

Next, the operation voltage waveforms will be described. Between bothends of each of the secondary coils 202 b and 202 c of the transformer202, there appears an alternating voltage impulse waveform as shown inFIG. 5C. The diodes 209 and 208 connected to the secondary coils 202 band 202 c point in opposite directions as described above, andaccordingly the voltage waveforms at the first discharge electrode 12 a,the first induction electrode 12 b, the second discharge electrode 13 a,and the second induction electrode 13 b relative to the groundingterminal, or in some cases relative to one side of the input powersource 201 (the reference potential, i.e., the side to which the diodes208 and 209 are connected), are as shown in FIGS. 5D, 5E, 5F, and 5G,i.e., positively or negatively biased versions of the waveform shown inFIG. 5C.

In the embodiment shown in FIG. 5A, the potentials at the firstdischarge electrode 12 a and the first induction electrode 12 b relativeto the grounding terminal, or in some cases relative to one side of theinput power source 201 (the reference potential, i.e., the side to whichthe diodes 208 and 209 are connected), are both positive. Thus, here, ofall the ions generated, negative ions are neutralized on the firstdischarge electrode 12 a, and positive ions are repelled and therebyreleased. On the other hand, the potentials at the second dischargeelectrode 13 a and the second induction electrode 13 b relative to thegrounding terminal, or in some cases relative to one side of the inputpower source 201 (the reference potential, i.e., the side to which thediodes 208 and 209 are connected), are both negative. Thus, here,negative ions are released.

On the other hand, in the embodiment shown in FIG. 5B, when theswitching relay 203 is switched to the selection terminal 203 a, thepotentials at the first discharge electrode 12 a and the first inductionelectrode 12 b relative to the grounding terminal, or in some casesrelative to one side of the input power source 201 (the referencepotential, i.e., the side to which the diodes 208 and 209 areconnected), are both positive. Thus, here, positive ions are generated.When the switching relay 203 is switched to the selection terminal 203b, however, the potentials at those same terminals relative to thegrounding terminal, or in some cases relative to one side of the inputpower source 201 (the reference potential, i.e., the side to which thediodes 208 and 209 are connected), are both negative. Thus, here,negative ions are generated. The potentials at the second dischargeelectrode 13 a and the second induction electrode 13 b relative to thegrounding terminal, or in some cases relative to one side of the inputpower source 201 (the reference potential, i.e., the side to which thediodes 208 and 209 are connected), are both negative. Thus, here,negative ions are released.

The positive ions are H⁺(H₂O)_(m) and the negative ions are O₂⁻(H₂O)_(n) (where m and n are natural numbers, and denote accompanimentby a plurality of H₂O molecules).

As described above, when the switching relay 203 is switched to theselection terminal 203 a, the ions generated from the first discharger12 are positive, and thus, together with the negative ions generatedfrom the second discharger 13, substantially equal quantities ofpositive and negative ions are generated. When substantially equalquantities of H⁺(H₂O)_(m) and O₂ ⁻(H₂O)_(n) are released into the air,those ions surround airborne mold spores and viruses floating in theair, and thus it is possible to deactivate them by the action of a freeradical, namely hydroxyl radical (.OH), generated as a result.

How this happens will be described in more detail below. When analternating-current voltage is applied between the electrodes of thefirst and second dischargers 12 and 13, oxygen or moisture in the airreceives energy and ionizes, producing ions consisting chiefly ofH⁺(H₂O)_(m) (where m is an arbitrary natural number) and O₂ ⁻(H₂O)_(n)(where n is an arbitrary natural number). These ions are released into aspace by a fan or the like. The ions H⁺(H₂O)_(m) and O₂ ⁻(H₂O)_(n)attach to the surface of airborne germs and, through a chemicalreaction, produce a free radical, namely H₂O₂ or (.OH). Since H₂O₂ or(.OH) exhibits extremely powerful reactivity, it is possible, bysurrounding bacteria present in the air with such a substance, todeactivate them. Here, (.OH) represents radical OH, a type of a freeradical.

On the surface of the cells of airborne bacteria, positive and negativeions undergo a chemical reaction expressed by Formulae (1) to (3) belowto produce a free radical, namely hydrogen oxide H₂O₂ or hydroxylradical (.OH). Here, in Formulae (1) to (3), m, m′, n, and n′ eachrepresent an arbitrary natural number. As a result, airborne bacteriaare destroyed by the decomposing action of the free radical. In thisway, it is possible to efficiently deactivate and remove airbornebacteria present in the air.

H⁺(H₂O)_(m)+O₂ ⁻(H₂O)_(n)→.OH+½ O₂+(m+n) H₂O   (1)

H⁺(H₂O)_(m)+H⁺(H₂O)_(m′)+O₂ ⁻(H₂O)_(n)+O₂ ⁻(H₂O)_(n′)

→2.OH+O₂+(m+m′+n+n′) H₂O   (2)

H⁺(H₂O)_(m)+H⁺(H₂O)_(m′)+O₂ ⁻(H₂O)_(n)+O₂ ⁻(H₂O)_(n′)

→H₂O₂+O₂+(m+m′+n+n′) H₂O   (3)

On the principle described above, by releasing positive and negativeions, it is possible to obtain an effect of deactivating airborne germsand the like.

The Formulae (1) to (3) above can produce a similar effect on thesurface of toxic substances present in the air. Thus, it is possible tooxidize or decompose toxic substances by the action of the free radical,namely H₂O₂ or (.OH). In this way, it is possible to make chemicalsubstances such as formaldehyde and ammonia substantially harmless byturning them into nontoxic substances such as carbon dioxide, water, andnitrogen.

Thus, by driving a blower fan, it is possible to release the positiveand negative ions generated by the ion generating element 1 out of thebody. Then, by the action of these positive and negative ions, it ispossible to deactivate mold and germs present in the air and therebysuppress their proliferation.

Positive and negative ions also have an effect of deactivating virusessuch as coxsackie virus and polio virus, and thus help prevent pollutionby such viruses.

Moreover, positive and negative ions have also been confirmed to have aneffect of decomposing odor-generating molecules, and thus help deodorizea space.

On the other hand, when the switching relay 203 is switched to theselection terminal 203 b, the ions generated from the first discharger12 are negative, and thus, together with the negative ions generatedfrom the second discharger 13, negative ions are generated from bothelectrodes. This is effective to supply a large quantity of negativeions into a space in which an excessive quantity of positive ions arepresent due to electric appliances or for other causes in a householdback to a state in which well-balanced quantities of positive andnegative ions are present as in a wild forest, or to obtain a relaxingeffect.

The voltage application circuit 20 has only to apply an alternatingvoltage waveform starting with the positive polarity and an alternatingvoltage waveform starting with the negative polarity respectivelybetween the first discharge electrode 12 a and the first inductionelectrode 12 b and between the second discharge electrode 13 a and thesecond induction electrode 13 b shown in one of FIGS. 2A, 2B, 3, 4A, 4B,and 8 to 11. Accordingly, the voltage application circuit 20 may beconfigured in any other manner than shown in FIGS. 5A and 5B; forexample, it may adopt a configuration shown in FIG. 12 or 13.

FIG. 12 shows a modified version of the circuit shown in FIG. 5B whichis so configured as to be more inexpensive and to require lesscomponents. To simplify the description, such components as are foundalso in the embodiment shown in FIG. 5B are identified with the samereference numerals. The voltage application circuit 20 shown in FIG. 12comprises, as a primary-side drive circuit, an input power source 201,an input resistor 204, a rectifying diode 206, a transformer driveswitching device 212, a capacitor 211, and a flywheel diode 213. In acase where the input power source 201 is commercially distributedalternating-current power, the voltage of the input power source 201charges the capacitor 211 through the input resistor 204 and therectifying diode 206. When the voltage here becomes higher than aprescribed voltage, the transformer drive switching device 212 turns onand applies the voltage to a primary coil 202 a of a transformer 202.Immediately thereafter, the energy accumulated in the capacitor 211 isdischarged through the transformer drive switching device 212 and theprimary coil 202 a of the transformer 202. This turns the voltage acrossthe capacitor 211 back to zero, and then charging starts again. In thisway, charging and discharging are repeated at prescribed time intervals.

The transformer 202 has, as a secondary-side circuit, two secondarycoils 202 b and 202 c, and these are connected respectively to the firstdischarge electrode 12 a, the first induction electrode 12 b, the seconddischarge electrode 13 a, and the second induction electrode 13 b shownin one of FIGS. 2A, 2B, 3, 4A, 4B, and 8 to 11. When the transformerdrive switching device 212 in the primary-side circuit turns on, theenergy on the primary side is transmitted to the secondary coils 202 band 202 c of the transformer, causing an impulse-shaped voltage toappear therein. It should be noted that, here, the secondary coils andthe electrodes are so connected that the polarity of the voltage appliedbetween the first discharge electrode 12 a and the first inductionelectrode 12 b is opposite to the polarity of the voltage appliedbetween the second discharge electrode 13 a and the second inductionelectrode 13 b.

To the first discharge electrode 12 a is connected not only thesecondary coil 202 b of the transformer 202 but also the cathode of adiode 209. The anode of the diode 209 is, through a relay 214, groundedor connected to one side (a line AC2, i.e., the reference potential) ofthe input power source 201. In a case where the input power source 201is commercially distributed alternating-current power, since one side ofthe commercially distributed alternating-current input power is groundedin Japan, connecting an electric appliance or the like without agrounding terminal to one side of the input power source 201 isequivalent to grounding it. To the second discharge electrode 13 a isconnected not only the secondary coil 202 c of the transformer but alsothe anode of a diode 208. The cathode of the diode 208 is grounded orconnected to one side (the line AC2) of the input power source 201.

Next, the operation voltage waveforms will be described. Between bothends of each of the secondary coils 202 b and 202 c of the transformer202, there appears an alternating voltage impulse waveform. Here, thevoltage waveform at the first induction electrode 12 b relative to thefirst discharge electrode 12 a is an alternating voltage waveformstarting with the positive polarity as shown in FIG. 14A, and thevoltage waveform at the second induction electrode 13 b relative to thesecond discharge electrode 13 a is an alternating voltage waveformstarting with the negative polarity as shown in FIG. 14B.

Moreover, since the secondary coil 202 c is connected through the diode208, which points in the forward direction, to the line AC2 (in somecases, to the grounding terminal). Thus, the voltage waveform at thesecond discharge electrode 13 a and the voltage waveform at the secondinduction electrode 13 b relative to the line AC2 are as shown in FIGS.15A and 15B, respectively, i.e., negatively biased versions of thewaveform shown in FIG. 14B. Accordingly, negative ions are generatedfrom the second discharger 13. The negative ions are O₂ ⁻(H₂O)_(n)(where n is a natural number, and denotes accompaniment by a pluralityof H₂O molecules).

On the other hand, when the relay 214 is on, the secondary coil 202 b isconnected through the diode 209, which points in the reverse direction,to the line AC2. Thus, the voltage waveform at the first dischargeelectrode 12 a and the voltage waveform at the first induction electrode12 b relative to the line AC2 are as shown in FIGS. 16A and 16B,respectively, i.e., positively biased versions of the waveform shown inFIG. 14A. Accordingly, substantially the same quantity of positive ionsas the negative ions generated at the second discharger 13 are generatedfrom the first discharger 12. The positive ions are H⁺(H₂O)_(m) (where mis a natural number, and denotes accompaniment by a plurality of H₂Omolecules).

FIG. 17A is a diagram showing the waveform shown in FIG. 14A or 14Balong a different time axis, and FIG. 17B is a diagram showing thewaveform shown in FIG. 16A or 16B along a different time axis. Thevoltage applied to each electrode has an impulse waveform that decays ina short time as shown in these figures. This results from the electricoscillation damping by the inductance and resistance of the transformerand the action of the flywheel diode 213. Specifically, the current thatis produced by the voltage induced in the primary coil 202 a by thecurrents flowing through the secondary coils 202 b and 202 c is made toflow back through the primary coil 202 a, the flywheel diode 213, andthe transformer drive switching device 212, and this quickly damps thevoltage oscillation that occurs in the secondary coil 202 b and thesecondary coil 202 c.

FIG. 18A is a waveform diagram showing the voltage waveforms at thefirst and second discharge electrodes 12 a and 13 a relative to the lineAC2 when the relay 214 is on, and are thus the same as FIGS. 15A and16A. FIG. 18B is a waveform diagram showing the voltage waveforms at thefirst and second discharge electrodes 12 a and 13 a relative to the lineAC2 when the relay 214 is off. When the relay 214 is on, as shown inFIG. 18A, the voltage waveform at the first discharge electrode 12 aindicated by line L1 is positively biased, and the voltage waveform atthe second discharge electrode 13 a indicated by line L2 is negativelybiased. When the relay 214 is off, as shown in FIG. 18B, while thevoltage waveform at the second discharge electrode 13 a indicated byline L2 is negatively biased as otherwise, the voltage waveform at thefirst discharge electrode 12 a indicated by line L1 is no longer biasedbut is now alternating. This is because, when the relay 214 is off, thesecondary coil 202 b is in a floating state. As a result of the firstwave being negative and the second and following waves having analternating waveform, both positive and negative ions are generated,though in small quantities.

Accordingly, when the relay 214 is off, the small quantities of positiveand negative ions generated from the first discharger 12 combined withthe large quantity of negative ions generated from the second discharger13 produce, as a while, a state rich in negative ions in which a verysmall quantity of positive ions and a large quantity of negative ionsare present. On the other hand, when the relay 214 is on, the positiveions generated from the first discharger 12 combined with the negativeions generated from the second discharger 13 produce a state in whichsubstantially equal quantities of positive and negative ions arepresent.

Thus, by releasing substantially equal quantities of H⁺(H₂O)_(m) and O₂⁻(H₂O)_(n) into the air, it is possible to surround airborne mold sporesand viruses present in the air with those ions and thereby deactivatethem by the action of a free radical, namely hydroxyl radical (.OH),produced as a result. Alternatively, it is possible to release a largequantity of negative ions into a space where an excessive quantity ofpositive ions are present due to electric appliances or for other causesin a household to restore a state in which well-balanced quantities ofpositive and negative ions are present as in a wild forest, or to obtaina relaxing effect. These modes of operation can be switched by turningthe relay 214 on and off.

The transformer 202 shown in FIG. 12 has its coils arranged as shown inFIG. 19. FIG. 19 is a diagram showing the arrangement of components inthe ion generating apparatus incorporating the transformer 202 shown inFIG. 12. In FIG. 19, reference numeral 220 represents an electrode panelportion where discharge electrodes (not illustrated) are formed,reference numeral 221 represents an electrode frame for keeping theelectrode panel portion 220 in a fixed position, reference numeral 222represents a molding material, reference numeral 223 represents acircuit board to which the transformer 202 is fixed and on which circuitcomponents are mounted, and reference numeral 224 represents a circuitcomponent mounting portion on which input/output connectors and othercircuit components are mounted.

The transformer 202 has the secondary coils 202 b and 202 c arranged onboth sides of the primary coil 202 a. Arranging the coils of thetransformer 202 in this way helps secure a distance between thesecondary coils 202 b and 202 c, and thus helps alleviate the directinfluence of the magnetic field generated by one secondary coil on theother. Thus, it is possible to alleviate the variation of the voltagesappearing in the two secondary coils as a result of their respectivemagnetic fields affecting each other, and thus it is possible to preventthe variation of the quantities of ions generated by the ion generatingelement to which the voltages appearing in those secondary coils areapplied.

FIG. 13 is a circuit diagram showing still another embodiment of thevoltage application circuit 20. To simplify the description, suchcomponents as are found also in the embodiment shown in FIG. 12 areidentified with the same reference numerals, and their explanations willnot be repeated. The voltage application circuit 20 shown in FIG. 13differs from the voltage application circuit 20 shown in FIG. 12 inthat, instead of the combination of one transformer 202 and a flywheeldiode 213, a combination of two transformers 215 and 216 and twoflywheel diodes 217 and 218 connected respectively to the primary coilsthereof is used In addition, in the primary-side drive circuit, thearrangement of the transformer drive switching device 212 and thecapacitor 211 is reversed.

In a case where the input power source 201 is commercially distributedalternating-current power, the voltage of the input power source 201charges the capacitor 211 through the input resistor 204, the rectifyingdiode 206, and the flywheel diodes 217 and 218. When the voltage herebecomes higher than a prescribed voltage, the transformer driveswitching device 212 turns on and applies the voltage to the serialcircuit consisting of a primary coil 215 a of the transformer 215 and aprimary coil 216 a of the transformer 216. Immediately thereafter, theenergy accumulated in the capacitor 211 is discharged through thetransformer drive switching device 212 and the serial circuit consistingof the primary coil 215 a of the transformer 215 and the primary coil216 a of the transformer 216. This turns the voltage across thecapacitor 211 back to zero, and then charging starts again. In this way,charging and discharging are repeated at prescribed time intervals.

The transformers 215 and 216 have, as a secondary-side circuit,secondary coils 215 b and 216 b, respectively, and these are connectedrespectively to the first discharge electrode 12 a, the first inductionelectrode 12 b, the second discharge electrode 13 a, and the secondinduction electrode 13 b shown in one of FIGS. 2A, 2B, 3, 4A, 4B, and 8to 11. When the transformer drive switching device 212 in theprimary-side circuit turns on, the energy on the primary side istransmitted to the secondary coils 215 b and 216 b, causing animpulse-shaped voltage to appear therein. It should be noted that, here,the secondary coils and the electrodes are so connected that thepolarity of the voltage applied between the first discharge electrode 12a and the first induction electrode 12 b is opposite to the polarity ofthe voltage applied between the second discharge electrode 13 a and thesecond induction electrode 13 b.

To the first discharge electrode 12 a is connected not only thesecondary coil 215 b of the transformer 215 but also the cathode of adiode 209. The anode of the diode 209 is, through a relay 214, groundedor connected to one side (a line AC2) of the input power source 201. Tothe second discharge electrode 13 a is connected not only the secondarycoil 216 b of the transformer 216 but also the anode of a diode 208. Thecathode of the diode 208 is grounded or connected to one side (the lineAC2) of the input power source 201.

The operation voltage waveforms of the voltage application circuit 20configured in this way as shown in FIG. 13 are the same as the operationvoltage waveforms (FIGS. 14A to 17A and FIGS. 14B to 17B) of the voltageapplication circuit 20 shown in FIG. 12, and therefore theirexplanations will not be repeated. The voltage application circuit 20shown in FIG. 13 is characterized in that the transformer 215 forapplying a voltage between the first discharge electrode 12 a and thefirst induction electrode 12 b and the transformer 216 for applying avoltage between the second discharge electrode 13 a and the secondinduction electrode 13 b are independent of each other, and in that, forthose transformers, the flywheel diodes 217 and 218 are providedrespectively.

In this configuration, the current produced by the voltage induced inthe primary coil 215 a by the current flowing through the secondary coil215 b simply flows back through the primary coil 215 a and the flywheeldiode 217, and thus does not influence the transformer 216. Likewise,the current produced by the voltage induced in the primary coil 216 a bythe current flowing through the secondary coil 216 b simply flows backthrough the primary coil 216 a and the flywheel diode 218, and thus doesnot influence the transformer 215. Thus, even when a load variation orthe like occurs in one discharger, the variation does not influence thevoltage applied to the other discharger. Thus, it is possible to preventvariation of the quantity of ions generated by the other discharger.

In the voltage application circuit 20 shown in FIG. 13, the primary coil215 a of the transformer 215 and the primary coil 216 a of thetransformer 216 are connected in series. It is, however, also possibleto adopt a circuit configuration in which they are connected inparallel.

The transformers 215 and 216 shown in FIG. 13 have their coils arrangedas shown in FIG. 20. FIG. 20 is a diagram showing the arrangement ofcomponents in the ion generating apparatus incorporating thetransformers 215 and 216 shown in FIG. 13. For convenience's sake, suchcomponents as are found also in FIG. 19 are identified with the samereference numerals. In FIG. 20, reference numeral 220 represents anelectrode panel portion where discharge electrodes (not illustrated) areformed, reference numeral 221 represents an electrode frame for keepingthe electrode panel portion 220 in a fixed position, reference numeral222 represents a molding material, reference numeral 223 represents acircuit board to which the transformers 215 and 216 are fixed and onwhich circuit components are mounted, and reference numeral 224represents a circuit component mounting portion on which input/outputconnectors and other circuit components are mounted.

The transformers 215 and 216 have the secondary coil 216 b, the primarycoil 216 a, the primary coil 215 a, and the secondary coil 215 barranged in this order. Arranging the transformers 215 and 216 in thisway helps secure a distance between the secondary coils 216 b and 215 b,and thus helps alleviate the direct influence of the magnetic fieldgenerated by one secondary coil on the other. Thus, it is possible toalleviate the variation of the voltages appearing in the two secondarycoils as a result of their respective magnetic fields affecting eachother, and thus it is possible to prevent the variation of thequantities of ions generated by the ion generating element to which thevoltages appearing in those secondary coils are applied.

In the above description, the transformer drive switching device 212shown in FIGS. 12 and 13 is assumed to be a no-gate, two-terminalthyristor (a “Sidac” manufactured by Shindengen Electric ManufacturingCo., Ltd., Japan). It is, however, also possible to adopt a slightlydifferent circuit configuration using a thyristor (SCR). The input powersource 201 may be a direct-current power source so long as the circuitis so configured as to operate in a similar way as described above. Thatis, the primary-side drive circuit of the circuit may be configured inany manner so long as it operates in a similar way.

Ion generating elements or ion generating apparatuses according to theinvention as described above can be incorporated in electric appliancessuch as air conditioners, dehumidifiers, humidifiers, air purifiers,refrigerators, fan heaters, microwave ovens, washer-driers, cleaners,and sterilizers. With such electric appliances, it is possible toachieve, in addition to the functions of the electric appliancesthemselves, the function of varying the quantity and balance of ions inthe air by operating the incorporated ion generating apparatus andthereby produce a desired environment in a room.

All the embodiments described above deal with cases in which a singleion generating element having a plurality of ion-generating dischargeris used to generate positive and negative ions separately and to releasethe two types of ions independently into a room. It should beunderstood, however, that the present intention may be implemented inany other manner; for example, it is possible to adopt a construction inwhich a plurality of ion generating elements are used to generatepositive and negative ions separately and to release the two types ofions independently into a room.

INDUSTRIAL APPLICABILITY

Ion generating elements and ion generating apparatuses according to thepresent invention can be used in various electric appliances such as airconditioners, dehumidifiers, humidifiers, air purifiers, refrigerators,fan heaters, microwave ovens, washer-driers, cleaners, and sterilizersthat are used chiefly in a closed space (i.e., in a house, in a room ina building, in a sickroom or operating room in a hospital, in a car, inan aircraft, in a ship, in a storehouse, or in a compartment in arefrigerator).

1. An ion generating element, comprising: a positive ion discharger forgenerating positive ions; and a negative ion discharger for generatingnegative ions, the ion dischargers arranged separately from andindependently of each other with a distance securing insulationtherebetween, wherein at least one of the dischargers includes adischarging portion for causing electric discharge, and a conductingportion having a voltage same as the discharging portion, the conductingportion surrounding a perimeter or part of the discharging portion. 2.An ion generating element, comprising: a positive ion discharger forgenerating positive ions; and a negative ion discharger for generatingnegative ions, the ion dischargers arranged separately from andindependently of each other with a distance securing insulationtherebetween, wherein at least one of the dischargers includes adischarging portion for causing electric discharge, and a conductingportion having a voltage same as the discharging portion, andsurrounding a perimeter or part of the discharging portion so as topartition the ion dischargers, one from the other.
 3. The ion generatingelement according to claim 1, wherein at least one of the positive andnegative ion dischargers has a pair of a discharge electrode and aninduction electrode arranged with a dielectric member in between theelectrodes.
 4. The ion generating element according to claim 2, whereinat last one of the positive and negative ion dischargers has a pair of adischarge electrode and an induction electrode arranged with adielectric member in between the electrodes.
 5. The ion generatingelement according to claim 1, wherein the positive ions generated by thepositive ion discharger are H⁺(H₂O)_(m) and the negative ions generatedby the negative ion discharger are O₂ ⁻(H₂O)_(n).
 6. The ion generatingelement according to claim 1, wherein the positive ions generated by thepositive ion discharger are H⁺(H₂O)_(m) and the negative ions generatedby the negative ion discharger are O₂ ⁻(H₂O)_(n).
 7. An ion generatingapparatus, comprising: the ion generating element according to claim 1;a voltage application circuit; and a blower for releasing the ionsgenerated by the positive and negative ion dischargers.
 8. An iongenerating apparatus, comprising: the ion generating element accordingto claim 2; a voltage application circuit; and a blower for releasingthe ions generated by the ion dischargers.
 9. The ion generatingapparatus according to claim 7, wherein the voltage application circuitgenerates positive ions by applying, to the positive ion discharger, avoltage waveform obtained by positively biasing an alternating-currentimpulse voltage, and generates negative ions by applying, to thenegative ion discharger, a voltage waveform obtained by negativelybiasing the alternating-current impulse voltage.
 10. The ion generatingapparatus according to claim 9, wherein the voltage application circuitgenerates positive ions by applying, to the positive ion discharger, avoltage waveform obtained by positively biasing an alternating-currentimpulse voltage, and generates negative ions by applying, to thenegative ion discharger, a voltage waveform obtained by negativelybiasing the alternating-current impulse voltage.
 11. The ion generatingapparatus according to claim 9, wherein the voltage application circuitincludes: a voltage application portion and a switching portion togetherswitchable between a mode in which the positive ions are generated byapplying, to the ion dischargers, the voltage waveform obtained bypositively biasing the alternating-current impulse voltage and a mode inwhich the negative ions are generated by applying, to the iondischargers, the voltage waveform obtained by negatively biasing thealternating-current impulse voltage, wherein operation is switchablebetween a mode in which approximately equal quantities of the positiveand negative ions are generated and a mode in which only the negativeions are generated.
 12. The ion generating apparatus according to claim10, wherein the voltage application circuit includes: a voltageapplication portion and a switching portion together switchable betweena mode in which the positive ions are generated by applying, to the iondischargers, the voltage waveform obtained by positively biasing thealternating-current impulse voltage and a mode in which the negativeions are generated by applying, to the ion dischargers, the voltagewaveform obtained by negatively biasing the alternating-current impulsevoltage, wherein operation is switchable between a mode in whichapproximately equal quantities of the positive and negative ions aregenerated and a mode in which only the negative ions are generated.